The APIs StringConcatFactory.makeConcat & makeConcatWithConstants when passed with MHs.publicLookup() errors out with StringConcatException. The documentation doesnt unambiguously mention restrictions on lookup param.

StringConcatFactory.makeConcat(MethodHandles.publicLookup(), "name", concatType); -> generates StringConcatException
whereas
StringConcatFactory.makeConcat(MethodHandles.lookup(), "name", concatType); -> works fine.

As per documentation:
"lookup - Represents a lookup context with the accessibility privileges of the caller" -> accessibility privileges can be spelt out more precisely. As in, of the PUBLIC/MODULE/PACKAGE/PRIVATE/PROTECTED privileges, what privileges the caller should hold to use the API.